Polyoxyethylene alkyl ether sulfate or alkyl ether sulfate, which is generally used as a sulfate surfactant, has extremely poor fluidity at a high concentration and is difficult to handle.
In order to solve this problem, Patent Document 1 proposes a surfactant composition formed by combining (a) polyoxyethylene alkyl ether sulfate or alkyl ether sulfate with (b) one or more of glyceryl ether or diglyceryl ether having an alkyl or alkenyl group having 4 to 24 carbon atoms and (c) a water-soluble salt, in which the content of the component (a) is not less than 40 wt. %.
Furthermore, Patent Document 2 proposes a surfactant composition formed by combining (a) a polyoxyethylene alkyl ether sulfate or alkyl sulfate with (b′) an alkylene oxide adduct of alcohol, represented by: R2O—(AO)m—R3, and (c) a water-soluble salt, in which the content of the component (a) is not less than 40 wt. %.
However, these surfactant compositions are not sufficiently satisfactory in terms of the fluidity after long-term storage at a low temperature (5° C.) and the foamability when diluted.